Well, since somebody needs to be that guy, at least one of those symbols, the Petrine Cross, is an explicitly Christian symbol, and the Ankh, though pagan in origin, had an uplifting meaning (“life” or “life to come”) that jived well with early Christian belief in the resurrection (of Jesus’s and the hope of their own), that they adopted and used it. Early Christians also independently developed and used the “crux ansata” which, looking very much like an ankh, was also a reason for the ankh’s adoption. Even the pentagram has been used as a Christian symbol. It’s been a symbol of a lot of things to a lot of cultures, and there are even multiple Christian meanings associated with it. Some of those were pagan, and predate Christianity, and some of those were alchemical or occult, and arose in the Renaissance or Enlightenment—basically whenever someone wanted to group five things together—but the idea that the “point down” version was explicitly evil didn’t come about until the 1800s. Basically, among Christians, only extreme iconoclasts or those ignorant of history would find any of those symbols offensive or demonic at all.